Fourteen suspected pirates from Somalia and Yemen were indicted by a U.S. federal grand jury in Virginia on Thursday in connection with the hijacking of a yacht last month that resulted in the deaths of four Americans.

The Justice Department says 13 suspected pirates from Somalia and one from Yemen were indicted on a range of charges that include piracy, kidnapping and the use of firearms during a crime.

If convicted, the suspects could be sentenced to life in prison.

The indictment of the alleged pirates stems from the hijacking of a yacht last month south of Oman in the Arabian Sea.

The four Americans on board were taken hostage and later killed as U.S. Navy officials tried to negotiate their release. U.S. Special Forces then captured the men.

Jean and Scott Adam owned the yacht. They died along with friends Bob Riggle and Phyllis Macay.

Attorney General Eric Holder

At a news conference on Wednesday, U.S. Attorney General Eric Holder told reporters that the Obama administration is determined to go after anyone who harms Americans anywhere in the world.

“We will protect our citizens," he said. "We will do all that we can to make sure that they are safe. And for those who would engage in acts that put them at risk or result in the deaths of American citizens, they will be held accountable in American courts.”

Holder was asked about the decision to prosecute alleged Somali pirates in U.S. courts, and whether he had a message for the pirates.

“If you attack American citizens, you are going to be held accountable and we will put you in jail for extended periods of time," he said. "And we will consider other measures. We will seek ultimate sanctions where that is appropriate.”

A U.S. conviction on a charge of piracy carries a mandatory penalty of life in prison. Conviction on the kidnapping charge could also lead to a sentence of life in prison.

The indictment does not include murder charges against any of the suspected pirates. But it says that at least three of the defendants who were aboard the yacht shot and killed U.S. citizens.

The incident in February marked the first time that Americans have been killed in the wave of pirate attacks and hijackings that have plagued the region in recent years.

In November, five Somali men were convicted on piracy charges related to separate attacks on two U.S. Navy ships last year that were part of an international flotilla protecting shipping in the waters off the East coast of Africa.